Low-friction rolling plunger for a wearable drug delivery device

ABSTRACT

Disclosed herein are various embodiments of a pump mechanism comprising a rigid structure having an open end and a closed end, a plunger disposed in the open end of the rigid structure, and a flexible, fluid-proof sheet of material attached to an inner wall of the rigid structure and bonded to the head of the plunger such as to form a fluid barrier between the interior of the rigid structure and the plunger. Movement of the plunger toward the closed end of the rigid structure causes a rolling corner to be formed between the head of the plunger and the rigid structure and a fluid contained within the pump chamber to be forced out of the pump chamber via a fluid port defined in the closed end of the rigid structure.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 63/234,759, filed Aug. 19, 2021, the contents of whichare incorporated herein by reference in their entirety.

BACKGROUND

Many conventional drug delivery systems, particularly systems whichinclude a wearable drug delivery device, include a drug container withinthe wearable drug delivery device, often referred to as a reservoir,that stores a liquid drug for delivery to a user via a patient interfacein accordance with an algorithm.

Such devices require a pump mechanism to move the liquid drug from thereservoir to the patient interface. The pump mechanism may be controlledby a microcontroller running software embodying an algorithm fordetermining an appropriate quantity of the liquid drug to dispense andto provide the proper signals to the pump mechanism to deliver thedesired quantity. The pump mechanism may comprise a driven plungerdisposed in a rigid enclosure. The plunger may be driven within theenclosure by any known means, for example, via a motor-driven leadscrewor other well-known mechanisms.

In certain prior art devices, the pump mechanism and the reservoir maybe integrated. The reservoir and pump mechanism may comprise a rigidstructure containing the liquid drug and having a plunger disposedtherein which forces the liquid drug from the reservoir to the patientinterface. In other prior art devices, the pump mechanism may beseparate from the reservoir and may be in fluid communication with thereservoir via a conduit, which may be, for example, a flexible conduit.In such cases, the reservoir may be composed of a flexible materialwhile the pump mechanism may be a rigid cylindrical structure having aplunger disposed therein such that when the plunger moves in onedirection, a suction is generated which draws the liquid drug from thereservoir into the pump chamber and, when the plunger moves in theopposite direction, pressure is generated within the pump chamber thatforces the liquid drug to the patient interface. Both the integratedreservoir/pump mechanism and the separate reservoir/pump mechanismprovide a way to dispense a liquid drug disposed in the reservoiraccurately and in a controlled manner.

Prior art versions of the pump mechanism utilize a dynamic sealingelement, usually one or more O-rings, disposed around an outercircumference of the plunger head and in frictional contact with aninner wall of the pump chamber or reservoir, to prevent fluid leakagebetween the plunger and the inner wall. There are several difficultiesassociated with the use of O-rings as a sealing mechanism. First, thereis an energy loss caused by the friction between the reservoir and theO-rings, which may cause the need for significant energy in the drivingmechanism to move the plunger. Because typical wearable drug deliverydevices powered by a battery, it would be desirable to reduce the energyrequirement for moving the plunger. Second, the use of the O-ringsimposes restrictions on the cross-sectional shape of the reservoir. Inreservoirs having cross-sectional shapes with sharp corners, the O-ringsin those areas provide unreliable sealing in the corner areas.Reservoirs having rounded (i.e. circular or ellipsoidal) cross-sectionalshapes may lead to lower volume efficiency. Lastly, there is asensitivity of the sealing performance to the quality and number ofO-rings, which makes a quality check during the manufacturing processnecessary.

Therefore, it would be desirable to provide an improved design for anintegrated reservoir and pump mechanism for a wearable drug deliverydevice that eliminates the need for O-rings, which would address thedifficulties identified above.

SUMMARY OF THE INVENTION

The embodiments of the invention described herein provide a design for apump mechanism that eliminates the difficulties associated with the useof the O-rings as a seal between the plunger head and the inner wall ofan enclosure, wherein the enclosure may be a reservoir or a pumpchamber. In a primary embodiment of the invention, a non-stretchable,flexible sheet of fluid-proof material is bonded to the head of theplunger. The edges of the flexible sheet are affixed to the inner wallof the enclosure or otherwise held at a fixed portion within theenclosure. As such, movement of the plunger within the pump chambercauses rolled corners to form in the flexible sheet between the head ofthe plunger and the inner wall of the enclosure. As the plunger moves tothe right or left within the enclosure, the rolled corners of theflexible sheet move along the inner wall of the enclosure and maintain aseal between the plunger and the inner surface of the enclosure

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional block diagram of an exemplary systemsuitable for implementing the example processes and techniques describedherein.

FIGS. 2A-2C show cross-sectional views of a first embodiment of theinvention showing three consecutive stages of the plunger motion.

FIG. 3 shows a cross-sectional view of a second embodiment of theinvention providing an implementation of the invention for reducing theholdup volume of fluid remaining in the reservoir.

FIGS. 4A-4B show a cross-sectional views of the third embodiment of theinvention providing an alternate implementation of the invention forreducing the holdup volume of fluid remaining in the reservoir.

FIG. 5 shows a cross-sectional view of an embodiment of the inventionwherein the pump mechanism is independent from the reservoir.

FIGS. 6A-6B show cross-sectional views of any one of the previousembodiments showing one method of driving the plunger within thereservoir.

DETAILED DESCRIPTION

The novel aspects of the embodiments of the present invention aredescribed in detail below. Several exemplary embodiments are shownherein; however, it should be realized that invention is not meant to belimited thereby but is instead meant to encompass the novel aspects ofthe various embodiments.

FIG. 1 illustrates a functional block diagram of a system examplesuitable for implementing the example processes and techniques describedherein.

The automatic drug delivery system 100 may implement (and/or providefunctionality for) a medication delivery algorithm, such as anartificial pancreas (AP) application, to govern or control automateddelivery of a drug or medication, such as insulin, to a user (e.g., tomaintain euglycemia—a normal level of glucose in the blood). The drugdelivery system 100 may be an automated drug delivery system that mayinclude a wearable automatic drug delivery device 102, an analyte sensor103, and a management device (PDM) 105.

The system 100, in an optional example, may also include a smartaccessory device 107, such as a smartwatch, a personal assistant deviceor the like, which may communicate with the other components of system100 via either a wired or wireless communication links 191-193.

The management device 105 may be a computing device such as a smartphone, a tablet, a personal diabetes management device, a dedicateddiabetes therapy management device, or the like. In an example, themanagement device (PDM) 105 may include a processor 151, a managementdevice memory 153, a user interface 158, and a communication device 154.The management device 105 may contain analog and/or digital circuitrythat may be implemented as a processor 151 for executing processes basedon programming code stored in the management device memory 153, such asthe medication delivery algorithm or application (MDA) 159, to manage auser's blood glucose levels and for controlling the delivery of thedrug, medication, or therapeutic agent to the user as well as otherfunctions, such as calculating carbohydrate-compensation dosage, acorrection bolus dosage and the like as discussed above. The managementdevice 105 may be used to program, adjust settings, and/or controloperation of the wearable automatic drug delivery device 102 and/or theanalyte sensor 103 as well as the optional smart accessory device 107.

The processor 151 may also be configured to execute programming codestored in the management device memory 153, such as the MDA 159. The MDA159 may be a computer application that is operable to deliver a drugbased on information received from the analyte sensor 103, thecloud-based services 111 and/or the management device 105 or optionalsmart accessory device 107. The memory 153 may also store programmingcode to, for example, operate the user interface 158 (e.g., atouchscreen device, a camera or the like), the communication device 154and the like. The processor 151, when executing the MDA 159, may beconfigured to implement indications and notifications related to mealingestion, blood glucose measurements, and the like. The user interface158 may be under the control of the processor 151 and be configured topresent a graphical user interface that enables the input of a mealannouncement, adjust setting selections and the like as described above.

In a specific example, when the MDA 159 is an artificial pancreas (AP)application, the processor 151 is also configured to execute a diabetestreatment plan (which may be stored in a memory) that is managed by theMDA 159 stored in memory 153. In addition to the functions mentionedabove, when the MDA 159 is an AP application, it may further providefunctionality to enable the processor 151 to determine acarbohydrate-compensation dosage, a correction bolus dosage anddetermine a basal dosage according to a diabetes treatment plan. Inaddition, as an AP application, the MDA 159 provides functionality toenable the processor 151 to output signals to the wearable automaticdrug delivery device 102.

The communication device 154 may include one or more transceivers suchas Transceiver A 152 and Transceiver B 156 and receivers or transmittersthat operate according to one or more radio-frequency protocols. In theexample, the transceivers 152 and 156 may be a cellular transceiver anda Bluetooth® transceiver, respectively. For example, the communicationdevice 154 may include a transceiver 152 or 156 configured to receiveand transmit signals containing information usable by the MDA 159.

The wearable automatic drug delivery device 102, in the example system100, may include a user interface 127, a controller 121, a drivemechanism 125, a communication device 126, a memory 123, a powersource/energy harvesting circuit 128, device sensors 184, and areservoir 124. The wearable automatic drug delivery device 102 may beconfigured to perform and execute the processes without input from themanagement device 105 or the optional smart accessory device 107. Asexplained in more detail, the controller 121 may be operable, forexample, implement the processes of the disclosed invention as well asdetermine an amount of insulin delivered, JOB, insulin remaining, andthe like. The controller 121 alone may implement the processes thedisclosed invention as well as determine an amount of insulin delivered,JOB, insulin remaining, and the like, such as control insulin delivery,based on an input from the analyte sensor 104.

The memory 123 may store programming code executable by the controller121. The programming code, for example, may enable the controller 121 tocontrol expelling insulin from the reservoir 124 and control theadministering of doses of medication based on signals from the MDA 129or, external devices, if the MDA 129 is configured to implement theexternal control signals.

The reservoir 124 may be configured to store drugs, medications ortherapeutic agents suitable for automated delivery, such as insulin,morphine, blood pressure medicines, chemotherapy drugs, or the like.

The device sensors 184 may include one or more of a pressure sensor, apower sensor, or the like that are communicatively coupled to thecontroller 121 and provide various signals. For example, a pressuresensor of the device sensors 184 may be configured to provide anindication of the fluid pressure detected in a fluid pathway between aneedle or cannula inserted in a user and the reservoir 124. For example,the pressure sensor may be coupled to or integral with a needle/cannulainsertion component (which may be part of the drive mechanism 125) orthe like. In an example, the controller 121 or a processor, such as 151,may be operable to determine that a rate of drug infusion based on theindication of the fluid pressure. The rate of drug infusion may becompared to an infusion rate threshold, and the comparison result may beusable in determining an amount of insulin onboard (JOB) or a totaldaily insulin (TDI) amount.

In an example, the wearable automatic drug delivery device 102 includesa communication device 126, which may be a receiver, a transmitter, or atransceiver that operates according to one or more radio-frequencyprotocols, such as Bluetooth, Wi-Fi, a near-field communicationstandard, a cellular standard, or the like. The controller 121 may, forexample, communicate with a personal diabetes management device 105 andan analyte sensor 103 via the communication device 126.

The wearable automatic drug delivery device 102 may be attached to thebody of a user, such as a patient or diabetic, at an attachment locationand may deliver any therapeutic agent, including any drug or medicine,such as insulin or the like, to a user at or around the attachmentlocation. A surface of the wearable automatic drug delivery device 102may include an adhesive to facilitate attachment to the skin of a useras described in earlier examples.

The wearable automatic drug delivery device 102 may, for example,include a reservoir 124 for storing the drug (such as insulin), a needleor cannula (not shown in this example) for delivering the drug into thebody of the user (which may be done subcutaneously, intraperitoneally,or intravenously), and a drive mechanism 125 for transferring the drugfrom the reservoir 124 through a needle or cannula and into the user.The drive mechanism 125 may be fluidly coupled to reservoir 124, andcommunicatively coupled to the controller 121.

The wearable automatic drug delivery device 102 may further include apower source 128, such as a battery, a piezoelectric device, other formsof energy harvesting devices, or the like, for supplying electricalpower to the drive mechanism 125 and/or other components (such as thecontroller 121, memory 123, and the communication device 126) of thewearable automatic drug delivery device 102.

In some examples, the wearable automatic drug delivery device 102 and/orthe management device 105 may include a user interface 158,respectively, such as a keypad, a touchscreen display, levers,light-emitting diodes, buttons on a housing of the management device105, a microphone, a camera, a speaker, a display, or the like, that isconfigured to allow a user to enter information and allow the managementdevice 105 to output information for presentation to the user (e.g.,alarm signals or the like). The user interface 158 may provide inputs,such as a voice input, a gesture (e.g., hand or facial) input to acamera, swipes to a touchscreen, or the like, to processor 151 which theprogramming code interprets.

When configured to communicate to an external device, such as the PDM105 or the analyte sensor 104, the wearable automatic drug deliverydevice 102 may receive signals over the wired or wireless link 194 fromthe management device (PDM) 105 or from the analyte sensor 104. Thecontroller 121 of the wearable automatic drug delivery device 102 mayreceive and process the signals from the respective external devices, aswell as implementing delivery of a drug to the user according to adiabetes treatment plan or other drug delivery regimen.

In an operational example, the processor 121 when executing the MDA 159may output a control signal operable to actuate the drive mechanism 125to deliver a carbohydrate-compensation dosage of insulin, a correctionbolus, a revised basal dosage or the like.

The smart accessory device 107 may be, for example, an Apple Watch®,other wearable smart device, including eyeglasses, provided by othermanufacturers, a global positioning system-enabled wearable, a wearablefitness device, smart clothing, or the like. Similar to the managementdevice 105, the smart accessory device 107 may also be configured toperform various functions including controlling the wearable automaticdrug delivery device 102. For example, the smart accessory device 107may include a communication device 174, a processor 171, a userinterface 178 and a memory 173. The user interface 178 may be agraphical user interface presented on a touchscreen display of the smartaccessory device 107. The memory 173 may store programming code tooperate different functions of the smart accessory device 107 as well asan instance of the MDA 179. The processor 171 that may executeprogramming code, such as site MDA 179 for controlling the wearableautomatic drug delivery device 102 to implement the disclosed inventionas described herein.

The analyte sensor 103 may include a controller 131, a memory 132, asensing/measuring device 133, a user interface 137, a powersource/energy harvesting circuitry 134, and a communication device 135.The analyte sensor 103 may be communicatively coupled to the processor151 of the management device 105 or controller 121 of the wearableautomatic drug delivery device 102. The memory 132 may be configured tostore information and programming code, such as an instance of the MDA136.

The analyte sensor 103 may be configured to detect multiple differentanalytes, such as lactate, ketones, uric acid, sodium, potassium,alcohol levels or the like, and output results of the detections, suchas measurement values or the like. The analyte sensor 103 may, in anexample, be configured to measure a blood glucose value at apredetermined time interval, such as every 5 minutes, or the like. Thecommunication device 135 of analyte sensor 103 may have circuitry thatoperates as a transceiver for communicating the measured blood glucosevalues to the management device 105 over a wireless link 195 or withwearable automatic drug delivery device 102 over the wirelesscommunication link 108. While called an analyte sensor 103, thesensing/measuring device 133 of the analyte sensor 103 may include oneor more additional sensing elements, such as a glucose measurementelement a heart rate monitor, a pressure sensor, or the like. Thecontroller 131 may include discrete, specialized logic and/orcomponents, an application-specific integrated circuit, amicrocontroller or processor that executes software instructions,firmware, programming instructions stored in memory (such as memory132), or any combination thereof.

Similar to the controller 121, the controller 131 of the analyte sensor103 may be operable to perform many functions. For example, thecontroller 131 may be configured by the programming code stored in thememory 132 to 1manage the collection and analysis of data detected thesensing and measuring device 133.

Although the analyte sensor 103 is depicted in FIG. 1 as separate fromthe wearable automatic drug delivery device 102, in various examples,the analyte sensor 103 and wearable automatic drug delivery device 102may be incorporated into the same unit. That is, in various examples,the sensor 103 may be a part of the wearable automatic drug deliverydevice 102 and contained within the same housing of the wearableautomatic drug delivery device 102 (e.g., the sensor 103 or, only thesensing/measuring device 133 and memory storing related programming codemay be positioned within or integrated into, or into one or morecomponents, such as the memory 123, of, the wearable automatic drugdelivery device 102). In such an example configuration, the controller121 may be able to implement the process the disclosed invention alonewithout any external inputs from the management device 105, thecloud-based services 111, another sensor (not shown), the optional smartaccessory device 107, or the like.

The communication link 115 that couples the cloud-based services 111 tothe respective devices 102, 103, 105 or 107 of system 100 may be acellular link, a Wi-Fi link, a Bluetooth link, or a combination thereof.Services provided by cloud-based services 111 may include data storagethat stores anonymized data, such as blood glucose measurement values,historical IOB or TDI, prior carbohydrate-compensation dosage, and otherforms of data. In addition, the cloud-based services 111 may process theanonymized data from multiple users to provide generalized informationrelated to TDI, insulin sensitivity, IOB and the like.

The wireless communication links 108, 191, 192, 193, 194 and 195 may beany type of wireless link operating using known wireless communicationstandards or proprietary standards. As an example, the wirelesscommunication links 108, 191, 192, 193, 194 and 195 may providecommunication links based on Bluetooth®, Zigbee®, Wi-Fi, a near-fieldcommunication standard, a cellular standard, or any other wirelessprotocol via the respective communication devices 154, 174, 126 and 135.

In certain embodiments, the controller of the device is composed of twoparts, the user application 160, which runs on the management device105, which may be, for example, a smartphone or a smart watch, and modelpredictive control (MPC) algorithm 130, which resides on the wearabledrug delivery device 102. This embodiment of the controller is capableof operation in both manual and automatic modes.

The MPC algorithm 130 provides insulin micro-boluses once every 5minutes based upon the predicted glucose over a 60-minute predictionhorizon. Optimal post-prandial control will require the user to givemeal boluses in the same manner as current pump therapy, but normaloperation of the MPC algorithm 130 will compensate for missed mealboluses and mitigate prolonged hyperglycemia. The MPC algorithm 130 usesa control-to-target strategy that attempts to achieve and maintain a settarget glucose value, thereby reducing the duration of prolongedhyperglycemia and hypoglycemia.

The user application 160 can be the primary user interface and will beused to start and stop a wearable drug delivery device 102, programbasal and bolus calculator settings for manual mode as well as programsettings specific for automated mode (hybrid closed-loop orclosed-loop).

In manual mode, the system 100 will deliver insulin at programmed basalrates and bolus amounts with the option to set temporary basal profiles.The controller will also have the ability to function as a sensoraugmented pump in manual mode, using sensor glucose data provided by theiCGM to populate the bolus calculator.

In automated mode, the system will support the use of multiple targetblood glucose values. For example, in one embodiment, target bloodglucose values can range from 110-150 mg/dL, in 10 mg/dL increments, in5 mg/dL increments, or other increments, but preferably 10 mg/dLincrements. The experience for the user will reflect current setup flowswhereby the healthcare provider assists the user to program basal rates,glucose targets and bolus calculator settings. These in turn will informthe MPC algorithm 130 for insulin dosing parameters. The insulin dosingparameters will be adapted over time based on the total daily insulin(TDI) delivered during each use of device 102. A temporary hypoglycemiaprotection mode may be implemented by the user for various timedurations in automated mode. With hypoglycemia protection mode, thealgorithm reduces insulin delivery and is intended for use overtemporary durations when insulin sensitivity is expected to be higher,such as during exercise.

System 100 includes two apps on a locked-down smartphone, referred to asPersonal Diabetes Manager (PDM) or Management Device or Controller 105:the user app 160. User app 160, will allow the use of large text,graphics, and on-screen instructions to prompt the user through theset-up processes and the use of system 100. It will also be used toprogram the user's custom basal insulin delivery profile, check thestatus, of device 102, initiate bolus doses of insulin, make changes toa patient's insulin delivery profile, handle system alerts and alarms,and enter automated mode.

The user app 160 may not directly communicate with one another. Instead,the iCGM transmitter will communicate EGV (estimated glucose values)directly to device 102. The transmitter number must be entered into theuser app 160, and this information is sent to device 102 to allowtransmission of EGV. Device 102 will pair directly to the transmitter toreceive EGV for the algorithm and also sends the EGV back to user app160.

The two-part controller provides the ability to calculate a suggestedbolus dose through the use of the bolus calculator. The bolus calculatorwill have the option for user selected population of the EGV, which iscommunicated to the app via device 102. This suggested bolus calculationfeature is provided as a convenience to the user to aid in determiningthe suggested bolus dose based on ingested carbohydrates, most recentsensor glucose reading (or blood glucose reading if using fingerstick),programmable correction factor, insulin to carbohydrate ratio, targetglucose value and insulin on board (JOB). IOB is calculated by thealgorithm taking into account any manual bolus and insulin delivered bythe algorithm.

Software related implementations of the techniques described herein mayinclude, but are not limited to, firmware, application specificsoftware, or any other type of computer readable instructions that maybe executed by one or more processors. The computer readableinstructions may be provided via non-transitory computer-readable media.Hardware related implementations of the techniques described herein mayinclude, but are not limited to, integrated circuits (ICs), applicationspecific ICs (ASICs), field programmable arrays (FPGAs), and/orprogrammable logic devices (PLDs). In some examples, the techniquesdescribed herein, and/or any system or constituent component describedherein may be implemented with a processor executing computer readableinstructions stored on one or more memory components.

The embodiments of the invention are directed to a low-friction rollingplunger that may be used in a combination reservoir/pump mechanism or ina separate standalone pump mechanism. The embodiments reduce thefriction between the plunger head and the inner wall of the chamber byeliminating the O-rings and substituting a rolling non-stretchable,flexible, fluid-proof sheet of material. In addition, thecross-sectional shape of the chamber may be any shape, including shapeshaving corners.

FIG. 2A shows a cross-sectional schematic view of an embodiment of acombination reservoir/pump mechanism. The pump chamber 214 is defined byrigid structure 202. Rigid structure 202 may have any cross-sectionalshape. Pump chamber 214 may be filled with a fluid and is in fluidcommunication with a patient interface (not shown) via fluid port 210.

Flexible sheet 204 may be any flexible material capable of containingthe fluid contained in pump chamber 214. In some embodiments, flexiblesheet 204 may be a fluid-proof or fluid-resistant fabric, for example,siliconized Kevlar® or Gore-Tex®. Flexible sheet 204 should have arelatively high tensile modulus, such as to be minimally stretchablewhile still being flexible. The edges of flexible sheet 204 are securedto the rigid structure 202 of the pump mechanism. In certainembodiments, an edge portion 208 of flexible sheet 204 may be clampedbetween a first portion 202 a and a second portion 202 b of rigidstructure 202 of the pump chamber 214, as shown in FIG. 3 . First andsecond portions 202 a, 202 b of rigid structure 202 may be securedtogether via a snap feature or by any other means known in the art, suchthat the edge portion 208 of flexible sheet 204 is clamped therebetween.In certain embodiments, flexible sheet 204 may be adhered to the innersurface of rigid structure 202 of pump chamber 244 via a heating orwelding process or via an adhesive. Flexible sheet 204 may also beadhered to or bonded to the head of plunger 206. In certain embodiments,flexible sheet 204 may be bonded to the head of plunger 206 via aheating or welding process. Flexible sheet 204 therefore forms a fluidbarrier between pump chamber 214 and the head of plunger 206.

The head of plunger 206 preferably has a shape substantially similar tothe cross-sectional shape of pump chamber 214. The head of plunger 206should be sized slightly smaller than the cross-sectional area of pumpchamber 214 such that movement of plunger 106 in direction “A” allowsflexible sheet 204 to form rolled corners 212 and does not bind flexiblesheet 204 between rigid structure 202 and the head of plunger 206. Tofurther prevent flexible sheet 204 from binding or aggregating ahead ofmoving plunger 206, flexible sheet 204 may be temporarily adhered to aninner surface of rigid structure 202, for example, via heating or spotwelding or via an adhesive, such that the flexible sheet 204 remains outof the way of the advancing plunger 206, but then, as plunger 206advances, the temporary adhesion between the flexible sheet 204 andinner surface of rigid structure 202 is overcome and trailing portionsof the flexible sheet are then able to advance with the moving plunger206. The portion of the flexible sheet 204 that may be temporarilyadhered to an inner surface of rigid structure 202 is a surface of theflexible sheet 204 that is not exposed to the drug inside chamber 214.

FIG. 2A shows the pump mechanism in a first state wherein plunger 206has not begun to move in direction “A”. FIG. 2B shows the pump mechanismas plunger 206 is moving in direction “A” and has traversed pump-chamber214 a portion of the way between the open end and the closed end ofrigid structure 202. As plunger 206 moves in direction “A”, flexiblesheet 204 forms rolled corners 212. The combined movement of plunger 206and the movement of flexible sheet 204 creates a pressure within pumpchamber 214, thereby forcing any fluid therein to a patient interfacethrough fluid port 210. FIG. 2C shows the pump mechanism in a statewherein plunger 206 has completed its movement in direction “A” and hastraversed the entire length of pump chamber 214, thereby forcing as muchof the fluid as possible to the patient interface via fluid port 210.

One difficulty that has been recognized and addressed by the inventorsis the inability to completely empty pump chamber 214. When the pumpmechanism is in the state shown in FIG. 2C2, holdup volume 216 willstill be filled with the fluid and it will not be possible to deliverthe holdup volume 216 of the fluid to the patient interface.

A second embodiment of the invention, which addresses the issue of theholdup volume, is shown in FIG. 3 . In this embodiment, pump chamber 214is provided with shoulders 302 which reduce the volume of the container214 in the area between the fluid port 210 and the area of the rigidstructure 202 where the edge portion 208 of flexible sheet 204 isconnected to rigid structure 202. The shoulder portion 302 eliminatesthe holdup volume 216 and should be narrow enough to allow the passageof the head of plunger 206 and the thickness of flexible sheet 204.Corners of the shoulders 302 may be tapered to guide plunger 206 pastthe corners and into the narrower portion of container 214, and toprevent any cutting or harm to flexible sheet 204 as flexible sheet 204traverses past the corners of shoulders 302. As with the firstembodiment, the head of plunger 206 should have a shape corresponding tothe cross-sectional shape of pump chamber 214. As can be seen in FIG. 3, a very small holdup volume 304 may remain however, this area can beminimized by a proper sizing of the flexible sheet 204. he length offlexible sheet 204 is slightly exaggerated in FIG. 2 to more clearlyshow how the flexible sheet 204 is inverted inside-out as plunger 206advances.

FIGS. 4A, 4B show a third embodiment of the invention showing a secondmethod for minimizing the holdup volume. In this embodiment, the pointof attachment of the edge portion 208 of flexible sheet 204 with rigidstructure 202 is moved as closely to the end of the pump chamber 214 aspossible. Portion 202 a of rigid structure 202, containing the fluidport 210, is shortened, while portion 202 b of rigid structure 202 ismade larger. Portions 202 a, 202 b of rigid structure 202 may connect toeach other in the same manner as discussed with respect to the previousembodiment. FIG. 4A shows the pump mechanism in a state wherein plunger206 has just begun to move in direction “A”, creating pressure withinpump chamber 214 to force a fluid contained therein to the patientinterface through fluid port 210. FIG. 4B shows the pump mechanism in astate wherein the plunger 206 has pushed as much of the fluid aspossible through fluid port 210. The head of plunger 206 should be shapeof the cross-sectional shape of pump chamber 214 and should allowpassage of the rolled corner 212 of flexible sheet 204 without bindingrolled corner 212 between the head of plunger 206 and the inner surfaceof rigid structure 202 of pump chamber 214. As explained above, flexiblesheet 204 may be temporarily adhered to an inner surface of rigidstructure 202, for example, via heating or spot welding or via anadhesive, such that the flexible sheet 204 remains out of the way of theadvancing plunger 206. As can be seen from FIG. 4B, the head of plunger206 must allow the passage of two thicknesses of flexible sheet 204between all edges of the head of plunger 206 and the inner surface ofrigid structure 202 of pump chamber 214. In this embodiment, only a verysmall holdup volume remains in the space within rolled corner 212 offlexible sheet 204.

FIG. 5 shows yet other embodiments of the invention in which pumpchamber 214 is part of a pump mechanism that is separate from thereservoir. In this embodiment, fluid may be drawn into the pump from areservoir via fluid port 210 or via a separate port adjacent to fluidport 210 (not shown) by movement of plunger 206 in direction “B”, whichcreates a suction within pump chamber 214 to draw the fluid from thereservoir. In this embodiment, pump chamber 114 may be much smaller thana volume of the reservoir. Once the fluid has entered pump chamber 214,plunger 206 moves in direction “A” to create pressure to force the fluidto the patient interface via fluid port 210. In such embodiments, fluidport 210, as well as the inlet port 502 connecting pump chamber 214 withthe reservoir, may each be provided with a one-way valve such that thesuction created by plunger 206 to draw the fluid from the reservoir andinto pump chamber 214 does not also draw fluid from the patientinterface into the pump chamber 214 via fluid port 210. Further, theone-way valves will allow the passage of the fluid to the patientinterface via fluid port 210 and will also prevent the fluid from beingforced back into the reservoir by the pressure applied by plunger 206.In this embodiment, it is necessary that flexible sheet 204 be adheredto or bonded to the head of plunger 206 such that when plunger 206 movesin direction “B”, flexible sheet 204 is drawn away from the end of pumpchamber 214 containing fluid port 210 to create the suction.

In yet another embodiment of the invention (not shown), flexible sheet204 could comprise the entire reservoir. In this embodiment, thereservoir would comprise a sealed bag of the flexible material 204having a portion adhered to a plunger 206 and a second portion definingthe fluid port 210. Movement of the plunger 206 would compress thesealed bag and force the fluid contained therein to the patientinterface via the fluid port 210. To avoid a large holdup volume ofliquid drug, expansion of the flexible bag may be limited or otherwiseconstrained by a portion of the one or more housings of the wearabledrug delivery device.

FIGS. 6A, 6B show a cross-sectional schematic view of an embodiment ofthe invention showing one possible method for driving plunger 206 backand forth in directions “A” and “B” within pump chamber 214 (or in someembodiments, such as those shown in FIGS. 2A-4B, only in direction “A”).The mechanism comprises a leadscrew 602 which, when rotated in eitherdirection, linearly translates a drive nut 604 in either directions “A”or “B”. Drive nut 604 is coupled to plunger 206 via linkage 606 suchthat, as drive nut 604 translates linearly in directions “A” or “B”,plunger 206 is also translated linearly in directions “A” or “B”respectively. Leadscrew 602 may be rotationally driven by any knownmeans, for example, via a motor or via a coupling to a shape memoryalloy.

FIGS. 6A, 6B show linkage 606 being bent at an angle such as to beenable the space-efficient positioning of leadscrew 602 and drive nut604 within the one or more housings of the wearable drug deliverydevice. As such, as shown in FIG. 6B, linkage 606 may pass through aslot defined in the rigid structure 202 of pump chamber 214 (forexample, in a bottom portion of rigid structure 202 in FIGS. 6A, 6B).Because flexible sheet 204 creates a fluid barrier between pump chamber214, containing the fluid, and the head of plunger 206 and the area ofpump chamber 214 behind the head of plunger 206, the slot may extendfrom the open end of pump chamber 204 to the point wherein the edgeportion 208 of flexible sheet 204 is attached to the rigid structure 202of pump chamber 214. Accordingly, leadscrew 602 need only extendapproximately 50% longer than a length of rigid structure 202 or pumpchamber 214, rather than 100% in some conventional systems.

In variations of the embodiment shown in FIGS. 6A, 6B, any method orapparatus may be used to linearly translate plunger 206 in directions“A” or “B” within pump chamber 214. For example, plunger 206 could bedriven by a motor connected to a scissor linkage. Other options are alsopossible.

The following examples pertain to various embodiments of the invention:

Example 1 is a reservoir having a rigid structure with an open end and aclosed end defining a fluid port, a flexible sheet attached to an innersurface of the rigid structure and a plunger disposed in the open end ofthe rigid structure having a head which is bonded to the flexible sheet.

Example 2 is an extension of Example 1, or any other example disclosedherein, wherein movement of the plunger toward the closed end of therigid structure causes the formation of a rolled corner of the flexiblesheet between the head of the plunger and an inner surface of the rigidstructure.

Example 3 is an extension of Example 1, or any other example disclosedherein, wherein the rigid structure has a first portion defining theclosed end of the rigid structure, a second portion defining the openend of the rigid structure wherein the flexible sheet is clamped betweenthe first and second portions.

Example 4 is an extension of Example 1, or any other example disclosedherein, wherein the flexible sheet is non-stretchable.

Example 5 is an extension of Example 4, or any other example disclosedherein, wherein the flexible sheet is composed of siliconized Kevlar® orGore-Tex®.

Example 6 is an extension of Example 3, or any other example disclosedherein, wherein the first portion has a cross-sectional area smallerthan the second portion such as to form a shoulder within the rigidstructure.

Example 7 is an extension of Example 1, or any other example disclosedherein, wherein the flexible sheet is attached to the rigid structure atthe closed end.

Example 8 is an extension of Example 1, or any other example disclosedherein, wherein the flexible sheet forms a fluid barrier between therigid structure and the plunger.

Example 9 is an extension of Example 8, or any other example disclosedherein, wherein the plunger is able to be linearly translated in eitherdirection within the rigid structure.

Example 10 is an extension of Example 8, or any other example disclosedherein, wherein linearly translating the plunger toward the closed endforces the fluid contained in the pump chamber out of the rigidstructure via the fluid port.

Example 11 is an extension of Example 8, or any other example disclosedherein, wherein linear translation of the plunger toward the open end ofthe rigid structure causes a suction within the pump chamber.

Example 12 is an extension of Example 9, or any other example disclosedherein, wherein the linear translation of the plunger is actuated by alinkage connected to a motor.

Example 13 is an extension of Example 12, or any other example disclosedherein, wherein the linkage has a rotationally-driven leadscrew, and adrive nut coupled to the plunger such that rotation of the leadscrewcauses a linear translation of the drive nut.

Example 14 is an extension of Example 13, or any other example disclosedherein, wherein the rigid structure defines a slot through which thelinkage may pass.

Example 15 is extension of Example 11, or any other example disclosedherein, wherein the linkage comprises a scissor mechanism.

Example 16 is an extension of Example 8, or any other example disclosedherein, wherein the rigid structure defines an inlet port in fluidcommunication with a reservoir such that suction caused in the pumpchamber by motion of the plunger draws fluid from the reservoir into thepump chamber.

Certain embodiments of the present invention were described above. Itis, however, expressly noted that the present invention is not limitedto those embodiments, but rather it is intended that additions andmodifications to the expressly described embodiments herein are also tobe included within the scope of the invention. Moreover, it is to beunderstood that the features of the various embodiments described hereinwere not mutually exclusive and can exist in various combinations andpermutations, even if such combinations or permutations were not madeexpress herein, without departing from the spirit and scope of theinvention. As such, the invention is not to be defined only by thepreceding illustrative description. Future filed applications claimingpriority to this application may claim the disclosed subject matter in adifferent manner and may generally include any set of one or morelimitations as variously disclosed or otherwise demonstrated herein.

1. A reservoir/pump mechanism comprising: a rigid structure having anopen end and a closed-end defining a fluid port; a flexible sheetattached to an inner surface of the rigid structure; and a plunger,disposed in the open end of the rigid structure.
 2. The mechanism ofclaim 1 wherein the flexible sheet is bonded to a head portion of theplunger.
 3. The mechanism of claim 1 wherein movement of the plungertoward the closed end of the rigid structure causes the formation of arolled corner of the flexible sheet between the head portion of theplunger and the inner surface of the rigid structure.
 4. The mechanismof claim 1 wherein the rigid structure comprises: a first portiondefining the closed end of the rigid structure; a second portiondefining the open end of the rigid structure; wherein the flexible sheetis attached to an inner surface of the rigid structure by being clampedbetween the first portion of the second portion when the first portionand second portion are joined together to form the rigid structure. 5.The mechanism of claim 1 wherein the flexible sheet has a high tensilemodulus such as to minimize the stretchability of the flexible sheet. 6.The mechanism of claim 1 wherein the flexible sheet is siliconizedKevlar® or Gore-Tex®.
 7. The mechanism of claim 4 wherein the firstportion has a cross-sectional area smaller than the second portion suchas to form a shoulder within the rigid structure that extends from anattachment point of the flexible sheet to the closed end of the rigidstructure.
 8. The mechanism of claim 1 wherein the flexible sheet isattached to the inner surface of the rigid structure at the closed endof the rigid structure.
 9. The mechanism of claim 1 wherein the flexiblesheet forms a fluid barrier between an interior of the rigid structureand the plunger, thereby forming a pump chamber within the rigidstructure which is only in fluid communication with the fluid port. 10.The mechanism of claim 9 wherein the plunger is able to be linearlytranslated within the rigid structure in a first direction toward theclosed end of the rigid structure and in a second direction toward theopen end of the rigid structure.
 11. The mechanism of claim 10 wherein alinear translation of the plunger toward the closed end of the rigidstructure forces a fluid contained in the pump chamber out of the rigidstructure via the fluid port.
 12. The mechanism of claim 10 whereinlinear translation of the plunger toward the open end of the rigidstructure causes a suction within the pump chamber to draw a fluid intothe pump chamber.
 13. The mechanism of claim 10 wherein the lineartranslation of the plunger within the rigid structure is actuated by alinkage connected to a motor.
 14. The mechanism of claim 13 wherein thelinkage comprises: a leadscrew rotationally driven by the motor; and adrive nut coupled to the leadscrew such that rotation of the leadscrewcauses a linear translation of the drive nut; wherein the drive nut iscoupled to the plunger.
 15. The mechanism of claim 14 wherein the rigidstructure defines a slot therein extending from the open end of therigid structure to a point wherein the flexible sheet is attached to theinner surface of the rigid structure, the slot allowing passage of thelinkage therethrough.
 16. The mechanism of claim 12 wherein the linkagecomprises a scissor mechanism linked to the motor.
 17. The mechanism ofclaim 9 wherein the rigid structure further defines an inlet port influid communication with the pump chamber and with a reservoircontaining a fluid, such that a linear translation of the plunger towardthe open end of the rigid structure causes a suction within the pumpchamber to draw the fluid from the reservoir into the pump chamber.